On Fri, Jun 30, 2017 at 8:56 AM, Simon King <si...@simonking.org.uk> wrote: > Your "sql time" measurement only includes the time it takes to send > the query to the database. I don't think it includes the time that the > database has to evaluate the query and return the rows. To measure > that, you ought to take the SQL string that the query produces, > execute that string outside of the ORM, and fetch all the rows back. > You should do that first with a bare PG connection, then with > SQLAlchemy Core, and compare those 2 times to the time you get with > the ORM. > > It's also worth noting that your query returns a lot of rows. I > haven't run your script, but it looks like you've got 254 > Registrations, each with 88 RegistrationData items, so that'll be > 22352 rows. For each of those rows, SA has to pick out the columns > representing the primary keys of the Registration, RegistrationData, > RegistrationFormFieldData and RegistrationFormItem classes, then check > them to see if they correspond to objects that are already in the > session. If they aren't, it has to construct those objects and link > them together. Processing 22352 rows in 0.91 seconds doesn't seem bad > to me.
Simon is correct here and the majority of that time is spent constructing Python objects from those rows. A full description of what you are observing, how to profile it, an a link to a full performance "example" suite, is at: http://docs.sqlalchemy.org/en/latest/faq/performance.html#how-can-i-profile-a-sqlalchemy-powered-application > > If you can reply with the bare PG and SA core timings, we may have a > better idea of how to optimise your query. > > Simon > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To post to this group, send email to sqlalchemy@googlegroups.com. > Visit this group at https://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
